On Jan 19, 4:39*pm, "Bob La Londe" wrote:
I finally decided to make a vacuum formed polystyrene cover for the encoder
on the front of the big mill. *Seems pretty straight forward. *I've got my
first vacuum box finished except for the port to put the vacuum hose in. *I
noticed a lot of the DIY guys make a hole for the smaller vacuum hose even
though they have a full size shop vac with the big hose. *Is there some
reason for that? *Seems to me that the larger port for the larger hose would
evacuate the box faster and form the plastic quicker before it cools. *Am I
missing something obvious?

(I have some PETG on the way to play with in case I don't like the way
polystyrene forms or holds up)

If this goes well, I have all kinds of ideas for vacuum forming...

Good vacuum pumps aren't cheap. I remember how expensive the one we
had at Qualcomm was. We used it all the time for holding thin parts on
fixtures we made. It broke in the middle of a job I was doing and I
tried to use a Shop-Vac. Learned a valuable lesson on why a good
vacuum pump is needed.